Machine tool power transmission and control mechanism



Oct. 2, 1945.

J. B. ARMITAGE ET AL MACHINE TOOL POWER TRANSMISSION AND CONTROL MECHANISM Filed Au fs, 1940' 10 Sheets-Sheet 1 INVENTORS' Oct. 2, 1945. J. B. ARMITAGE r AL 2,385,907

MACHINE TOOL; POWER TRANSMISSION AND CONTROL MECHANIS'M Filed Aug 3, 1940 10 SheetsSheet 2 INVENTORS: JOJA'PM 555mm a ATTORNEY Oct. 2, 1945.

J. B. ARMITAGE ET 1. 2,385,907

MACHINE TOOL POWER TRANSMISSION AND CONTROL MECHANISM l0 Shets-Sheet 3 Filed Aug. 5, 1940 ATTORNEY.

Oct. 2, 1945. J.- B. ARMITAGE ETAL ,9

MACHINE TOOL POWER TRANSMISSION AND CONTROL MECHANISM Filed Aug. 3, 1940 10 Sheets-Sheet 4 IHHIIIMIII INVENTORS: MIPHJ-IRM M 1".

ggwffi ATTORNEY.

Oct. 2, 1945. J. B. ARMITAGE ET AL 2,385,907

' MACHINE TOOL POWER TRANSMISSION AND CONTROL MECHANISM Filed Aug. 3, 1940 10 Sheets-Sheet 5 ATTORNEY.

1945- J. B. ARMI'YI'AGE- ET AL 2,385,907

MACHINE TOOL POWER TRANSMISSION AND CONTROL MECHANISM Filed Aug. '3, 1940 1o Sheets-Sheet 6 I I l Ig 1].- INVENTORS."

awn a-mw/ 65 a; 57 7: -5.: mauv- ATTORNEY.

Oct. 2, 1945. J. B. AR MITAGE ET AL 2,385,907

MACHINE TOOL POWER TRANSMISSION AND CONTROL MECHANISM Filed Aug. 3, 1940 10 Sheets-Sheet '7 l 1 7 115 In ATTORNEY;

Oct. 2, 1945. J. B. ARMITAGE ETAL 2,385,907

MACHINE TOOL POWER- TRANSMISSION AND CONTROL MECHANISM I Filed-Mug 3, 1940' 10 Sheets-Sheet 8 ATTORNEY.

Oct. 2, 1945;

J. B. ARMITAGE ET AL MACHINE TOOL POWER TRANSMISSION AND CONTROL MECHANISM 10 Sheets-Sheet 9 Z w z N 2 m a m P 6 1... :MJ a mi E. 6 0 WFflM J 1 M m E v M wm flm %W m x. d 3 .\w H E d a mm. a E F 0 M U m w M 8 k a 65 VIVA v 88 J.\'N/ & a 76 5 O W M 2 w w w 4. Z 0 U/ w .w n m v 7 26 wmw Z ()ct- 1945- J. B. ARMITAGE ET AL 2,385,907

MACHINE TOOL POWER TRANSMISSION AND CONTROL MECHANISM Filed Aug. 3, 1940 10 Sheets-Sheet 10 BY: W WM TTORNEY.

Patented Oct. 2, 1945 MACHINE TOOL POWER TRANSMISSION AND v CONTROL MECHANISM Joseph B. Armitage and Theodore F. Eserkaln, Wauwatosa, Wis., assignors to Kearney & Trecker Corporation, West Allis, Wis., a corporation of Wisconsin Application August 3, 1940, Serial No. 356,666

33 Claims.

This invention relates generally to machine tools and more particularly to improved mechanism for transmittingpowerto and for controlling its effect upon various actuating elements of a machine tool.

A general-object of the invention is to provide improved .power transmitting and controlling mechanism for actuating the movable parts of a machine tool.

Another object of the invention is to provide an improved hydraulically actuated control system for regulating the operation of a machine tool.

Another object is to'provide an improved control system for the main driving mechanism of a machine tool that is arranged to be operated hydraulically either by action of a control lever on the frame of the machine or by action of a' control lever carried by a movable element of the machine.

Another object is to provide an hydraulically actuated main clutch controlling system for a milling machine arranged to be operated by a clutch lever at a rear control station on the machine column or by a clutch lever at a front control station on the movable knee of the machine.

Another object is to provide an improved hydraulic control system for a machine tool arranged to cause disengagement of the main driving clutch prerequisite to a shifting operation and functioning to prevent reengagement of the clutch by action of the shifting lever following the shifting operation.

Another object is to provide a millingmachine of the vertical spindle type, in which the 'main clutch is controlled by a shifting lever carried on the movable vertical-head of the machine.

Another object is to provide an improved speed I indicating apparatus for a machine tool.

Another object is to provide an improved range change shifting mechanism for a machine tool.

Another object is to provide an improved speed changing mechanism arranged to be turned slowly while being shifted either in response to movement of a shifting lever on the machine frame or in response to movement of a shifting lever on a movable element of the machine.

Another object is to provide ,an improved slow speed drive mechanism for facilitating gear shifting, in which a hydraulic actuating cylinder is carried by the element supporting the slow'speed driving clutch.

Another object is to provide means for controlling the slow speed driving arrangement from a shiftinglever on the sliding milling machine.

head of a vertical Another object is to provide improved driving mechanism for moving the vertical head of a milling machine.

According to this invention, a milling machine is provided with an improved power transmission and control mechanism including a'control system for shifting the main driving clutch, arranged to be operated hydraulically from a plurality of sources. For manual control of the machine, the hydraulic clutch controlling system maybe actuated either by lever on the column of the machine or by a lever carried by the movable knee of the machine. For automatic control, the main clutch actuating mechanism is interlocked with the speed changing 'mechanism in such manner that the clutch is moved to disconnecting position by the hydraulic control system upon unlatching movement of either a speed changing gear shifting lever or a range changing gear shifting lever. To avoid unintentional starting of the machine after a speed changing operation, the system is arranged to prevent reengagement of the main clutch upon relatching movement of either shifting lever, restarting of the machine being possible only under, the positive control of the operator by actuation of one or the other of the manually operated clutch controlling levers. The hydraulic control system furthermore effects engagement of an improved slow speed driving arrangement to turn the transmission mechanism slowly for facilitating the gear shifting operation. In a machine of the horizontal type, the range changing lever cooperates with a speed indicating dial associated with the speed changing lever, the dial presenting two series of indicia alternately arranged and angularly displaced relative to each other for cooper-- ating with an indicator on the range changing lever at angularly spaced positions. In a machine of the vertical spindle type, the range changing mechanism is carried in the sliding vertical head and a mechanical connection is arranged between the range changing mechanism in the head and the hydraulic control system-in the column for effecting disengagement of the main clutch and engagement of the slow speed drive upon unlatching movement of the muse change shifter. In this instance the angularly spaced positions associated with the speed dial areindicated by characters identified with the two positions assumed by the range changing shifter on the sliding head.

The inventionis exemplified herein by embodiments illustrated in connection with a general representation of a typical machine tool structure; however, it is to be understood that the The foregoing and other objects of this invention, which will become more fully apparent from the following detailed specification, may be achieved by the particular apparatus that is depicted in and described in connection with the accompanying drawings, in which;

Figure 1 isa view in left side elevation of a vertical spindle milling machine exemplifying amachine tool in which the features of the present invention may be incorporated to advantage.

Fig. 2 is a view in right side elevation of the same machine, parts having been broken away to show some of the internal mechanism.

Fig. 3 is a developed view generally in vertical I section through themachine, taken along the line 3 3 in Fig. 2 and showing the driving mechanism; 7

Fig. 4 is an enlarged fragmentary view of the clutch actuating linkage shown inFig. 3;

Fig. 5 is a fragmentary view of another part of the transmission mechanism, taken generally in vertical section along the line 5-5 in Fig. 1;

Fig. 6 is a fragmentary view in vertical section through the upper part of the milling machine, showing the spindle driving mechanism? Fig. 7 is a view in vertical transverse section through the upper part of the machine showing the spindle driving and feeding mechanism, taken along the line 11 in Fig. 8;

Fig. 8 is a view in horizontal section through the spindle supporting and driving structure taken along the-line 8-8 in Fig. 7;

Fig. 9 is a, fragmentary view in right side elevation of the spindle head tripping mechanism shown in Fig. 8;

Fig. 10 is a view in left side elevation of the upper portion of a milling machine of, the horizontal spindle type, showing the speed indicating mechanism and other features utilized in this type of machine;

Fig. 11 is a fragmentary view in vertical section of the range changing mechanism for the horizontal ,type machine, taken along the, line llll inFig. 10;

Fig. 12 is an enlarged detailed view, partly in vertical section, of a splined connecting sleeve shown in Fig. 10';

Fig. 13 is a view of the connecting sleeve taken partly in transverse section along the line l3i3 in Fig. 12; p

Fig. 14 is a fragmentary plan view of the work supporting structure with parts broken away to show the transmission and control mechanism;-

Fig. 15 is an enlarged fragmentary, somewhat diagrammatical view illustrating the operation of the feed screw and nut adjusting mechanism shown in Fig. 14;

Fig. 16 is a fragmentary view, showing the details of the nut adjusting mechanism;

Fig. 17 is a transverse sectional view of the Fig. 19 is a view in vertical section along the line |9-l9 in Fig. 18;

Fig. 20 is a schematic diagram of the hydraulic control system for actuating the clutch and brake mechanism;

Fig. 20a is an end view of a-handle portion of Fig. 20; and

Fig. 21 is a schematic diagram of a modified form of the hydraulic control system.

The machine tool shown generally in Figs.

1 and 2 of the drawings as exemplifying a preferred embodiment of the invention, is a milling machine of the vertical spindle, knee and column type, although it is to be understood that various of the inventive features set forth herein may be incorporated in and utilized with advantage in machines of different construction.

Referring more specifically to the drawings, and particularly to Figs. 1 and 2 thereof, the milling machine there shown comprises essentially an upstanding hollow column 20 formed integrally with a forwardly projectingbase 2| and constituting a supporting frame carrying the cooperating work supporting and tool supporting elements of the machine.

The work supporting element of the machine includes a knee structure 23 mounted on the front face of the column 20 for vertical sliding movement therealong and carrying a saddle structure head. 21 slidably mounted for vertical movement in cooperating relationship with the work tablev 25.

Power for moving the slidably mounted work supporting'elements and for rotating the cuttersupporting spindle, is derived from a motor 30, indicated in Fig. 3, that is preferably mounted in the baseof the column 20. From the motor 30, the power is transmitted to a main drivingpulley 3|, by means of multiple belts 32, the motor being. accessible by opening a louvered door 33 on the left side of the machine and the belt driving mechanism being enclosed by a door 34 on the right side of the machine. The main pulley 3| may be connected selectively, by means of a main disconnecting friction clutch 35,.to

screw and nut adjusting mechanism, taken along the line |1|1 in Fig. 16;

Fig. 18 is a fragmentary view showing the main clutch and brake controlling levers and their interconnecting linkage;

transmit powerthrough a main driving shaft 36 to a speed changing and reversing mechanism 31 (shown in Fig. 5) housed within the column and generally similar in construction-and operation to the mechanism shown in copending application Serial No. 146,581; filed June 5 1937, that issued May 6, 1941, as Patent No. 2,240,973.

From the speed changer 31, power is transmit? ted by means of a vertical shaft 38 and ahorlzon tal gear train 39 mounted in the-top of the col- '4 umn as shown in Fig. 6, to a vertically disposed splined shaft 4| which is joumalled in the sliding head 21 for vertical movement therewith whilemaintaining. driving connection ,with the gear train 39 in the overhanging forward end of the column. Within the sliding head 21, the

shaft 4| transmits power to the vertical spindle 28 by means of a range changing mechanism 42, whereby the spindle may be operated in either a high speed range or a low speed range.

As appears in Figs. 6, 1 and 8, the spindle driving range changing mechanism includes a relatively large gear wheel 45 fixed on the spindle 28 and a relatively small gear wheel or pinion 46 likewise fixed on the spindle 28 the pinion 46 being positioned below and spaced from the large gear wheel 45. Disposed in cooperating constant meshing engagement with the pinion 46 on the spindle 28 is a relatively large driving gear wheel 41 that is rotatably mounted concentrically with the driving shaft 4|, the teeth of the gear wheel 41 and of the pinion 46 being preferably of helical or spiral type. For selecting the range of operation, there is slidably splined on the shaft 4| a shifting pinion 49 that is adapted when in its upper position of operation, to mesh with the large gear wheel 45 on the spindle 28, and when in its lower position of operation to interlock with internal teeth 50 formed in the upper end of the hub of the driving gear wheel '41 to thereby effect a driving connection between the shaft 4| and i the driving gear wheel 41.

For shifting the range changing pinion 49, there is provided a rotatably and axially movable shifting shaft shown in Figs. 7 and 8, that is journalled in horizontal position in the sliding head 21. Manually actuatable lever means for moving the shaft 5| is provided by an actuating handle or knob member 52 on the end of the shaft that projects at the front of the sliding head 21, as appears in Figs. 1, 8 and 20. As shown in Fig. 8, the shaft 5| is provided with a pinion element 53 that meshes with a cooperating rack 54 formed on a vertically slidable shifting fork 55 that engages a. shifting ring 56 fixed on the pinion 49, in manner to provide for vertical sliding movement of the pinion upon rotary movement of the shaft 5|. For maintaining the shiftable'pinion 49 in either of its operating positions, the shifting handle 52 is provided with a pair of inwardly projecting lugs 51, as shown in Fig. 20, the lugs beingarranged to engage either of two pairs of complementary latching holes in the face of the head 21. The handle 52 is further provided with an indicating pointer 58 adapted to indicate the fast or slow position of the range change pinion by characters on the front of the head, asshown in Fig. 20a.

Upon axial unlatching movement of the range changing shaft 5|, a hydraulic control system in the column 20 is actuated, by means of connecting mechanical linkage, to cause disengagement of the main driving clutch 35 and engagement of an auxiliary slow speed driving connection for facilitating the shifting operation. Asappears in Figs. '1, 8 and 20, the shaft 5| is provided with a circular rack 60 cooperating with apinion 6| on the lower end of an extensible shaft mechanism 62. The extensible shaft 62 constitutes a rotatable and slidable mechanical connection between the range changing shifter in'the sliding head 21 and 'a hydraulic control valve 63 mounted in the upper part of the column 26 the valve being provided with a valve piston '64 that is engaged for operation by an arm 65 fixed on the upper end of the extensible shaft mechanism 62. The valve 63 in the top of the column associated with the range changing mechanism constitutes part of a hydraulic control system that includes a generally similar valve 66 associated with. a speed changing lever 61 mounted on the left side of the 1937, now Patent No. 2,240,973, dated May 6, 1941.

The hydraulic control system functions in manner similar to that of the system disclosed in copending application Serial No. 255,848, filed February 11, 1939, now Patent No. 2,345,171, dated March 28, 1944, in that unlatching movement of either the range changing control handle 62 or the speed changing lever 61 prerequisite to a range changing or speed changing shifting movement, causes the main clutch 35 to be shifted to disconnecting position and a slow speed drive mechanism to be engaged for facilitating gear changing, in the manner set-forth and claimed in Reissue Patent No. He. 21,434.

As is indicated diagrammatically in Fig. 20, fluid pressure for-the hydraulic control system is derived from a pump 16 that withdraws hydraulic fluid, for instance lubricating oil, from a sump 1| through ajconduit 12, the sump 1| and the pump 10 being disposed in that part of the hollow column 26 which houses the speed changing mechanism 31.

From the pump 10, the hydraulic fluid under pressure flows through a conduit 13 to a port 14 in the range changer actuated valve 63 and thence through an interconnected opening to a port 15 from which a conduit 16 leads to port 11 in the speed changer actuated valve 66. As shown, the port 11 in the valve 66 is in communication with a port 18 from which a conduit 19 leads to a port ,inthe casing of aclutch actuating control valve 8|. The clutch controlling valve 8| is provided with a valve piston 82 that is arranged to be actuated either hydraulically, as the result of movement of the control valve 63 or 66, or manually by means of either of two clutch controlling levers, one being mounted on the column of the machine and the '83 is fixed on the outer end of a control shaft 84 iournalled in the side of the column as best shown in Figs. 18 and 20, the shaft carrying an arm 85 from which a pin 86 projects into an elongated actuating notch 81 in the side of the valve plunger 82, whereby the plunger may be moved longitudinally within the valve casing 8| by sidewise rocking movement of the lever 83, the valve being mounted in the side wall of the column above the shaft 84.

The other of the clutch controlling levers, designated 88, is pivotally mounted on the right side of the movable knee 23 near the front thereof and in the region of the forward control position, as shown in Fig. 2. The lever 88 is carried on a shaft 89 having a depending crank arm 90 which engages one end of a connecting link 9| extending rearwardly within the knee toward the column 26. At its inner end, the connecting link "9| is provided with rack teeth 92 (as shown in 88 on one end of a transverse controlshaft 81. The transverse shaft 8'! is provided at its left end with a gear segment 88 that meshes with a similar gear segment 88 fixed on the inner end of the control shaft 84, the arrangement being such that when the clutch controlling lever 88 on the knee is actuated, it causes the control shaft 84 and its connected clutch lever 83 to move, thereby actuating the clutch controlling valve piston 82 as previously explained. For counterbalancing the weight of the lever 88 on the knee, the connecting link Si is provided with a compression spring I8I acting indirection tending to move the lever 88 upward. With the clutch-controlling lever 83 in position A, shown in full lines in Fig. 20, the valve plunger 82 is so positioned that a groove I83 therein establishes communication between the pressure port 88 and a port I84 from which a conduit I85 leads to the lower end of a clutch actuating cylinder I88 for exerting pressure upon the lower face of a cooperating piston I81 therein. Pressure'on the lower side of the piston I8'I moves it upward within the cylinder I88, and exerts force through a piston rod I88 attached to the piston and depending from the cylinder, upon one arm of a bell crank I88, as best shown in Fig. 3. The cylinder I85 and the bell crank I88 are so positioned within the column 28 that the other arm of the bell crank I89 engages a shifting collar 8 that is operatively connected, as shown in Fig. 3, to actuate the main clutch 85, the arrangement being such that when the piston I 81 is moved upwardly, the main clutch 35 is engaged to eifect a driving connection between the driven pulley 3I and the main shaft 38 of the transmission mechanism within the column 28. Any liquid that may be trapped in the upper end of the cylinder I85 as the piston I8'I moves upwardly is expelled. through a conduit II2 that leads from the upper end of the cylinder to a port H3 in the casing of the valve 8|. The port I I3 communicates with'an opening II 4 extending longitudinally through the valve piston 82 and having communication, in the position shown, with a port H5 in the valve casing. From the port II5, a conduit (Heads to a port II! of a relay valve II8 provided with a spring urged plunger II9, a groove I28 in which establishes communication from the port I II to an exhaust port I2I that is open to the atmosphere.

When the clutch actuating piston I81 arrives at its upper position, it uncovers a port I24 in the wall of the cylinder I88, as shown'in Fig. 20, thereby permitting the hydraulic fluid flowing into the cylinder through the conduit I85 to escape into a conduit I25. The conduit I25 leads to a port I25 in the clutch controlling valve 8| which communicates through a groove IT! in the valve piston 82 with a port I28 that is connected to the lubricating system of the machine, the arrangement, being such that after the clutch 35 hasbeen shifted to engaged position, the oil under pressure from the pump 18 flows freely through the-control system into the lubricating system. 1

lfnow either of the clutch controlling levers 83 or 88 is moved to position B, indicated in full lines in Figs. 18 and 19, the clutch controlling valve piston 82 is moved to a position causing disengagement of the main clutch 35 and engagement ofa .brake I38 on the main driving shaft 38, for stopping rotation of the transmission mechanism. As shown in Fig. 19, the clutch controlling levers are retained in the position to .whlch they are shifted, by means of a spring urged plunger I3I which engages either of two notches or detents in the arm 85 on the control shaft 84 in manner to retain the valve plunger 82 in either the clutch engaging or the brake engaging position. With the valve plunger 82 in position B, the pressure port 88 is connected, by means of the groove I83, with the port II3 through which the pressure fluid then flows into the conduit II2 leading to the upper end of the cylinder I86 to exert pressure on the piston I87 in direction to move it downward. As the piston I81 moves downward, the fiuid in the lower end of the cylinder escapes through the conduit I85 to the port I84 which then communicates through a groove I33 in the piston 82 with the port II5, from which the conduit I I6 leads to the relay valve H8 and the open atmospheric port I2I.

In the event that it should become necessary to stop the machine suddenly, as in an emergency for example, the brake may be engaged more firmly by moving either of the clutch controlling levers to a third position, C, indicated in dotted lines. This causesfurther movement of the valve piston 82 to the left, from the position shown in Fig. 20, a sumcient distance to move the groove I21 out of register with the port I28, thereby cutting off communication with the lubricating system and permitting the full pressure of the hydraulic system to-be exerted upon the piston I81 for engaging the brake firmly. The maximum pressure which may be exerted in the hydraulic system is limited by a relief valve I38 that is connected to the conduit I3 leading from the pump I8 and that may be adjusted to establish a predetermined maximum pressure for the system. Any liquid which may be trapped in the left end of the valve 8 I when the plunger 82 is moved to the left, escapes through an axial opening I31 in the plunger which then communicates with a port I38 in the side of the valve case ing that is open to the atmosphere. 7

s As appears in Figs. 3 and 20,. the clutch actuating piston rod I88 is provided with a detent roller I38 that cooperates with a spring pressed detent plunger I48 to retain the clutch shifting mechanism in either the clutch engaging or the brake engaging position. Referring now to Fig. 3, the clutch shifting collar I I8 which is engaged by the bell crank I88, is fixed on a clutch and brake shifting rod I4I that is disposed concentric with and is movable endwise through the hollow main driving shaft 36, the rod being associated at its outer end with a toggle mechanism I42 for actu-- position to engage and exert clamping pressure upon an axially movable friction element I45 of the clutch. The clamping relationship between the arms I48 and the clutch member I45 may be adjusted by turning the ring I44 on the threaded hub, a spring pressed retaining pin I48 being provided for retaining the ring in its adjusted position. Each of the actuating arms I48 When the piston I81 arrives at its lower position, it uncovers a port I34 in the wall of the is pivotally connected. at its outer end to one end of a link I41 that is in turn pivotally connected at its other end to an actuating member I48 mounted on the outer end of the actuatin rod I. With the rod MI in its left or inner position, as shown in Fig. 4, the toggles constituted by the arms I43, the links I41 and the member I48, are in broken position, thereby ree leasing the arms I43 from clamping engagement with the clutch member I45. When the clutch actuating rod MI is moved to the right by movement of the actuating piston I 01 to the top of the cylinder I06, the member I48 is moved to the position shown in Fig. 3. .This moves the toggles past their center positions and causes the arms I43 to clamp the clutch member I45 for engaging the clutch, the clamping Iorce then tending to move the rod I4I further to the right. At this.

point, abutments on the ends oi. the links I41 engage the edge of the member I48 to lock the toggles, thereby preventing further movement oi the rod HI and releasing the bell crank I09 from the necessity of exerting force upon the collar I I0. The piston I01 now being in contact with the top of the cylinder I06, the collar H is relieved from pressure and is free to turn with the shaft As shown in the drawings, the actuating rod I4I has threaded engagement with the actuating member I48, the threads on the rod being of the same pitch as those on the hub of the clutch that engage the carrier ring I44. By thisarrangement, the actuating member I48 is caused to progress along the rod I. an amount equal to that which the carrier ring I44 progresses along the hub'of the clutch when the toggle mechanism is turned for adjusting the clutch. Accordingly, the relationship between the actuating member. I48 and the arms I43 of the toggle mechanism I42 remains the same regardless of adjusting movement of the toggle mechanism relative to the clutch friction element I45. Since movement of the clutch actuating mechanism in direction to engage the clutch is limited by abutment of the piston I01 with the top of the cylinder 106, this arrangement for retaining-fixed relationship in the actuating linkage is of especial importance.

If now a range changing shifting movement, for example, is to be eflected, the shifting knob 52 on the sliding head is first moved forward in unlatching movement to disengage the lugs 51 from the locking holes in the spindle head 21.

This causes the circular rack 60 on the range changing shaft 5| to turn the pinion 6I onthe lower end of the extensible shaft 62, thereby moving the valve piston 64 to the right from the position seen in Fig. 20. A cannelure I50 in the valve piston 64 with which the pressure port 14 communicates, is thereby moved out of communication with the valve port and into communication with a port I5I, whereupon pressure liquid flowing from the pump 10 through the conduit 13 andthe port 14 may pass along the cannelure I50 to the port I5I and thence through a conduit I52 to a port I53 of the valve 66 associated with the speed changer. The port 153 communicates permitting movement of the piston to the right beyond the position it assumes when the clutch controlling lever is moved to position A. With the valve plunger 82 in its right position, the longitudinal opening II4 therein is moved out of communication with the port H5 in order to prevent the escape of liquid from the upper end of the clutch actuating cylinder I06 through the conduit I II2, the ports H3 and H5, and the conduit II6 to the exhaust port I2I.

From the pressure cylinder I58, at the left end of the clutch controlling valve 6|, a pressure conduit I60 continues to-a pressure cylinder I6I in the lower end of the relay valve- I I8, the pressure therein causing the plunger II9 thereof to be moved upwardly against the resistance of a spring I62. This results in uncovering a port I63 through which the pressure fluid flows from the cylinder I6I into a conduit I64 leading to an inlet opening' I65 in the clutch actuating cylinder I06 which communicates with a cannelure I66 in the piston rod I08. From the cannelure I66; the pressure fluid flows along an axially disposed passageway I61 through the piston rod I08 into the middle of the-piston I01, and thence through a transverse passageway I68 into a cylindrical valve chamber I69 formed longitudinally in the piston I01 parallel with and at one side of the piston rod I08. Within the valve chamber I69 there is arranged a stationary valve plunger I10 adapted to register with and close the transverse passageway I68 when the piston I01 is positioned at a predetermined neutral point in its path of travel, the valve plunger I10 being provided with extending stems disposed to engage the respective ends'of the cylinder I06 to retain the plunger in predetermined position relative to the cylinder.

With the machine in operation, the main clutch being engaged and the clutch actuating piston I01 being in its upper position as shown, when a gear shifting operation is initiated, pressure through a cannelure I54 of a valve plunger I55 in the valve 66, with a port l56gfrom which a the valve piston 82 in direction to move it to the right, the actuating slot81 in the piston being of such length as to provide clearance or lost motion fllll admitted through the conduit I64, flows from the transverse passageway I68 through the valve chamber I69 to the upper end of the cyl inder I06 thereby exerting pressure to move the piston I01 downward. Since the port 15 in the valve 63 is now closed, no pressure is applied to the lower side of the piston I01 through the conduits 16, 19 and I05, nor can any liquid escape by this path. Likewise, no liquid can escape from the top of the cylinder through the conduit II2 by reason of the port II5 being closed. Liquid remaining in the lower end of the cylinder I06 then escapes through a port I13 in the cylinder wall which communicates with a conduit I14 leading to a port I15 in the relay valve I I8. With the relay valve piston H9 in its upper position, the port I15 is in communication with the groove I20 through which the liquid may exhaust into the atmosphere by way of the exhaust port -I2I. As the clutch actuating piston I01 descends within the cylinder I06, it has a tendency to travel beyond its predetermined neutral position, How,

ever, in doing so it will close the port, I13 thereby trapping liquid in the lower end of the cylinder and preventing further downward movement of the piston to the position in which the brake would be engaged.

- When the piston I01 arrives at the point atmechanism engaged, but the brake I30 has not yet been engaged. At this point the top of the piston partially exposes the upper port I34 in the cylinder wall thereby permitting the escape of any excess liquid which may enter the upper end of the cylinder, into the conduits I35 and I25 leading to the lubrication system.

When the piston I01. is thus retained in its neutral position, a port I18 extending from the transverse passageway I88 through the side of the piston, registers with a port I19 in the cylinder wall from which a conduit I80 leads to a 'port I8I in the relay valve II8. With the relay valve plunger H9 in its upper position, a groove I82 therein effects communication between the port MI and the port II1 from which the conduit I I6 leads to a conduit I83 that communicates with an actuating cylinder I84 for the slow speed driving mechanism. The port H5 in the valve casing 8| at the end of the conduit H6 is closed, preventing the escape of pressure.

therein to force it outwardly against one end of a pivoted lever arm I88.

As appears in Fig. 3, the cylinder I84 is formed in a, supporting bracket I81 to which the lever arm I86 is pivotally connected and that also carries a slow speed driving mechanism designated generally I80. The slow speed driving I88 is generally similar to the mechanism disclosed in the previously mentioned Patent No. 2,345,171, and comprises es sentially a, gyratory speed reduction gear mechanism I89 arranged to be driven by a gear train including a gear wheel I90 fixed on a sleeve I9I that is connected with and is continuously driven by the main driving pulley 3|. A friction clutch I92 is arranged to effect driving connection between the speed reducing .mechanism I89 and a gear train including a gear wheel I,93'fixed on the main driving shaft 36 of the machine.

When a shifting operation is initiated by unlatching movement of either the range changing knob 52 or the speed changing lever 81 and both the main clutch 35 and the brake l30, are moved to disengaged position to release the main driving shaft 36 for free rotation, pressure applied to the cylinder I84 moves the piston I85 outwardly against the lever arm I86, causing it' to pivot in manner to exert force inwardly upon a clutch actuating member I95 for engaging the clutch I92 to couple the slow speed driving mechanism I88 to the main shaft 36. Since the slow speed driving mechanism I88, the pivoted lever I86, and the cylinder I84 are all associteed with the bracket I81 in manner to constitute a unit, a fixed relationship is maintained between the actuating cylinder I84 and the clutch actuating element I95 regardless of any variations which may occur in the relationship between various major elements of the machine in assembling the mechanism in the column 20.

With the clutch actuating piston I01 in its neutral position, the detent roller I39 is disposed relative to the detent plunger I40, in such position that the plunger exerts force in direction tending to move the piston downward to brake engaging position, this force being resisted by the fluid trapped in the lower part of the cylinder. After the range changing operation has been completed, the shifting knob 52 is returned to latched position, thereby returning the valve plunger 64 to the position shown in Fig. '20. This results in interrupting the connection between the presusre port 14 and the port I5I from which the conduit I52 leads through connecting passages to the pressure cylinder I 58 in the valve 8| and the pressure cylinder I6I in the valve H8, the port I5I being then placed in communication with a port I91 that is open to the atmosphere. Pressure in the valve operating cylinders I58 and I6I is there by relieved, the valve plunger 82 remaining in its extreme right position, beingretained therein by means of a light detent mechanism I98, and the valve plunger II9 of the relay valve II8, being .retumed by the spring I62 to its lower position shown in Fig. 20. This results in closing the connection from the port I13 in the cylinder I06 through the conduit I14 and port I15 to the atmospheric port I2I, and also in closing the connection from the central slow speed port I19 through the conduit I80 and port 7 I8I to the port II1 of the relay valve II8 from which the conduits H6 and I83 lead to the slow speed clutch actuating cylinder I84. The port H1 is then connected through .the groove I 20 with the atmospheric pprt I2I for relieving pressure from the cylinder I84, thereby permitting the slow speed clutch I92 to return to disengaged position.

With the range change valve plunger 64 in the latched position as shown in Fig, 20, the pressure port 14 is again connected with the port 15 from which the pressure fluid flows through conduit 16, ports 11 and 18 and conduit 19 to the pressure port in the valve 8I. With the valve plunger 82 remaining'in the right position, the port 80 has communication with the port H3 thereby permitting the pressure flow to flow through the conduit I I2 to the upper end of the cylinder I06 to prevent the piston I01 from moving upward into clutch engaging position. This prevents the main driving clutch 35 from being reengaged unintentionally at the conclusion of a gear changing operation, restarting of the machine being possible only under positive control of the operator through actuation of either of the clutch controlling levers 83 or 88.

When it is desired to restart the'machine, one of the clutch controlling levers is first moved to the stop position B to withdraw the valve plunger 82 from its right position. The lever is then returned to'start position A, thus taking up the lost motion provided by the elongated actuating slot 81 and positioning the valve plunger 82 in the clutch engaging position A.- This completes the circuit from the pressure port 80 through the port I04 and conduit I05 to the lower end of the cylinder I06 for moving the piston I01 upward to clutch engaging position, as previously explained.

When it is desired to effect a speed changing operation by means 0! the speed changing lever 61, a latching handle 20I on this lever is drawn outward to uhlatch the lever for rotation. The

18 from which the conduit 18 leads to the pressure port 88 or the valve 8|, and to connect the pressure port 11 to the port I56 from which the conduit I51 leads to the actuating cylinder I58 of the valve 81. This moves the valve plunger 82 to the right for effecting automatic disengagement of the main clutch 35 and engagement of the slow speed driving clutch I92, as previously explained, the entirecycle or operations being similar to that initiated by unlatching movement of the range changing control knob 52.

In the event that the gears are shifted to change the setting of either the speed changing mechanism or the range changing mechanism when the spindle clutch is disengaged and the clutch controlling valve plunger 82 is in stop position (position B), it is preferable that the valve plunger 82 remain in this position in order to avoid unnecessary movement of the clutch controlling levers. Accordingly, the valve plunger 82 is so arranged that when it is in the left or stop position; it closes the connection between the conduit I51 and the pressure cylinder I58. Consequently, when either the range changing valve plunger 64 or the speed changing valve plunger I55 is moved in connection with a speed changing operation, the pressure fluid admitted from the pump 18 into the conduit I51 continues past the valve 8I into the conduit I68 without moving the valve plunger 82. Pressure in the conduit I68 then flows into the lower end of the relay valve I I8 and moves the plunger I I9 thereof upward as previously explained. This closes the connection between the conduit H6 and the exhaust port I2I and permits the pressure fluid to flow through port I63 into conduit I64 and through the inlet opening I65 into the cannelure I66 and passageway I61 in the piston rod I88. From the passageway I 61, the fluid flows through the transverse passageway I68 into the valve chamber I69 which then communicates with the lower end of the cylinder I86 since the piston I81 is now in the lower or brake engaging position. The pressure fluid in the lower part of the cylinder I86 then causes the piston I81 to move upward to the neutral or central position. As the piston I81 moves upward, fluid in the upper part of the cylinder I86 escapes through the port I34, the conduits I55 and I25, and the ports I26 and I28 into the lubrication system. When the neutral position is reached, the valve plunger I18 closes the transverse passageway I68 as previously explained, and the piston closes the port I34 to trap the remaining fluid in the upper end of the cylinder to prevent further upward movement of the piston.

Pressure fluid then flows from the passageway I68 through the port I18 and the registering port I19 into the conduit I88 leading to the relay valve H8. The relay valve plunger H9 being in its upper position, the conduit I88 communicates through ports I8I and H1 withthe conduit II6 that connects with the conduit I83 leading to the slow speed drive mechanism actuating cylinder I84 as previously explained. However in this instance the conduit II6 is already connected through the port I I of valve. 8I, groove I33 and port I84,with the conduit I85 leading directly to the lower end of the cylinder I86 and pressure from this source operates to engage the mechanism for turning the gearing slowly as soon as the cgnnection with the exhaust port I2I is closed by upward movement of the relay plunger H8.

Since during the time that the piston I81 is in neutral position for gear shifting, the detent roller I39 is in a position in which the detent plunger I48 exerts force upon it to move the piston rod I88 downward to brake engaging position, the brake will be reengaged automatically after the gear changing operation is completed. When the actuating valve plunger 64 or I55 is returned to latched position after a gear changing operation, pressure in the conduit I51 is relieved through the exhaust port I91 of valve 63. This permits relay valve plunger II9 to return to its lower position thereby establishing communication between port H1 and exhaust port I2I. Fluid pressure in the slow speed cylinder I84 then escapes through the exhaust port I2I and the slow speed drive disengages. Likewise, fluid In the lower part of the cylinder I86 escapes through'the conduit I and ports I84 exhaust port I2I, thereby permitting the piston I81 to move downward and engage the brake, pressure being admitted meanwhile to the upper part of the cylinder through the valves 63 and 66, conduit 18, pressure port 88 and the conduit II2.

In a modified form of the. hydraulic control system, shown in Fig. 21, the pressure conduit 19 leading from the speed changer actuated valve 66 is connected to lat central pressure port 286 in a modified clutch" controlling valve 281, the valve being provided with a valve plunger 288 that may be moved to clutch engaging or to brake engaging positions at opposite sides, re-.

spectively, of the neutral position shown in the drawing. As shown. the valve plunger 288 is provided with a medial groove 289 disposed to,

have communication with the pressure port 286 in any position assumed by the plunger. With the plunger 288 in the neutral position, pressure fluid entering the.port 286 from the conduit 18 flows through a longitudinal bore 2 in the plunger to a groove 2I2 thereon which communicates with a port 2I3 constituting a connection with the lubrication system, ithe arrangement being such that when the valve plunger is in neutral position, the oil'under pressure flows directly through the valve into the lubrication system.

For actuating the clutch controlling valve in the plunger cooperating with'a closely fitting slot in the lever for'this purpose. Furthermore, the two detent notches utilized in connection with the previously described clutch lever system are in this instance replaced by a single detent notch that functions to urge the valve plunger 288 to its neutral position at all times. As shown, the single detent notch 2I6 is formed in an overhanging end of the control lever 2I4 and cooperates with a spring pressed detent plunger 2I1 disposed to urge the lever to central position.

It now the clutch controlling lever 2| 4, is actuated to move the valve plunger 288 downward to the clutch engaging position, the groove 2I2 is moved out of register with the lubrication port 2I3, thereby preventing escape of the pressure fluid into the lubricating system. At the same time, the groove 209 communicating with the pressure port 206 is moved into communication with a port 2I8 from which a conduit 2I0 leads to the lower end of the clutch actuating cylinder I06, the fluid pressure being exerted on the lower side of the piston I 01 to move it upward to clutch engaging position. Liquid in the upper' spring pressed detent plunger 2 I 1 to act upon the notch H6 in manner to return the valve plunger 208 to its central position. This results in reestablishing connection from the pressure port 206 through the groove 209, the bore 2| I and the groove 212 with the lubrication port 2I3, and in closing both the port 218 connected with the lower end of the cylinder I06 and the port 22I connected with the upper end of the cylinder,

thereby preventing the flow of liquid into or out of either end of the cylinder and locking the piston I01 in clutch engaging position:

If now the clutch controlling lever 2 is moved to the brake engaging position, thereby moving the valve plunger 208 upward, the groove 2I2 is again moved out of communication with the lubrication port 2I3 to prevent escape of the liquid, and the pressure groove 209 is then moved into communication with the port 22I through which the pressure fluid flows into the conduit 220 and thence into the upper end of the cylinder I06. At the same time, a groove 225 in the valve plunger 208 establishes communication from the port 218 to an atmospheric port 226 for permitting the escape of liquid from the lower end of the cylinder I06 by way of the conduit 2I9. Pressure exerted by the fluid entering the upper end of the cylinder I06, causes the piston I01 to be moved downward to brake engaging position, whereupon the hand lever 2I4 may again be released to return to neutral position, thereby reestablishing communication from the pressure port 206 to the lubrication port 2I3 as before explained, and closing the ports 2I8 and HI communicating with the ends of the cylinder I06 to lock the piston I01 in the brake engaging position. I

If it is desired to effect a speed changing operation, for example by actuating the lever 61 to adjust the speed changing mechanism 31 either with the clutch actuating piston I01 in brake engaging position or with the clutch engaged and the machine operating, the latching handle 20I is first withdrawn thereby moving the valve plunger I55 of the valve 66 to the right. This disconnects the pressure port 110f the valve 66 from the port 18 from which the conduit 19 leads to the pressure port 206 of the clutch actuating valve 201, the pressure port 11 being then placed in communi'cation with the port I56 from which a conduit 228 leads to the port I65 of the clutch actuating cylinder I06. From the port I65, the pressure fluid flows through the cannelure I66, the longitudinal passageway I61, and the transverse passageway I68 into the valve chamber I69 from which it flows, as previously explained, into the one or the other end. of the cylinder I06 for moving the piston I01 from either the brake engaging or the clutch engaging position to a neutral position in which the valve plunger I10 closes the transverse opening I68.

With the piston I01 in the neutral or central position in which both the clutch and the brake are disengaged, the upper and lower edges of the piston partially uncover ports 230 and 23I formed I in the wall of the cylinder I 06, both of which communlcate with a conduit 232 that leads to a port 233 in the valve 201 which has communication, when the valve piston 208 is in its neutral position, through the groove 222 with the atmospheric port 223. By this arrangement, any pressure which may be developed in either end of the cylinder I06 is permitted to escape to atmosf phere without moving the piston I01 from its neutral position.

As previously explained, when the piston I01 is in its neutral position, the radial port I18 therein establishes communication from the transverse passageway I66 to the port I16 in the wall of the cylinder I06. -In the present instance, a conduit 235 efiects a direct connection from the port I19 to the cylinder "4 for exertin pressure therein upon the piston I85 to engage the clutch I92 of the slow speed drive mechanism, the arrangement being such that the slow speed clutch I92 can not be engaged until both the main clutch 35 and the brake I80 are disengaged by movement of the piston I01 to its neutral position. To prevent the slow speed drive mechanism from continuing to operate when either the main clutch 35 or thebrake I30 is engaged by actuation of the manually operated clutch controlling lever 40 either the clutch engaging or the brake engaging from the end of the plunger, the passageway having communication with both grooves and bein .open to the atmosphere.

In a milling machine of the horizontal spindle type, such as is illustrated in Fig. 10, the range cha g mechanism is disposed adjacent to the speed changing mechanism and is controlledfrom the left side of the column. As in the vertical machine, the range changer is provided with. a

control valve that is functionally similar to the control valve 63 shown in Fig. 20, and that is associated with thespeed changer actuated valve 66, in the manner set forth in the previously mentioned Patent No. 2,345,171. As appears in Figs. 10 and 11, the range changing mechanism for the horizontal type machine includes a large gear wheel 245 and a pinion 246 both rigidly fixed on a horizontally disposed spindle 241 in spaced arrangement. Cooperating with the spindle gear and pinion is a sliding gear couplet 240 constituted by a large gear wheel 249 and a pinion 250 adapted to be meshed respectively with the pinion 246 and the large gear wheel 245.

The mechanism for shifting the range change couplet 240 includes a shifting fork 252adapted to engage a groove 253 in the hub of the gear 243 and arranged to be moved by a crank arm 264 that is operatively connected by gearing 256-101 assessor actuation by a range changing lever 28' disposed on the side of the machine above the speed changing lever 61. The range changing lever 2" is mounted to be moved through a half revolution, from the horizontal position shown in full lines in Fig. to the horizontal position shown in dotted lines, a latching handle 254 being provided for latching the lever in either position, The latching handle functions upon unlatching movement thereof to shift the range changer actuated control valve 63, as in the case of unlatching movement of the range changing knob 52.

Associated with and operated by the speed changing lever 61 is a speedindicating dial 2 presenting two series of speed indicia corresponding with the two ranges of operation, the indicia of the two series being arranged alternately and those of one series being displaced angularly relative to those of the other series. The range changing lever 256 carries an indicator 2" that is disposed, when the lever 256 is in the position shown in full lines, to cooperate with one series of the indicia on the dial 260 for indicating the several spindle speeds obtainable by actuation of the speed changing lever 61 with the range changing lever 256 in the low range position. When the range changing lever 2 56 is moved to the high range position, shown in dotted lines, a

second indicator262 on the other side of the lever is positioned to cooperate with the other series of indicia for indicating the speeds obtainable in the high speed range, the angular displacement between the two series of indicia being such as to compensate for the displacement between the indicators 26l and 262 in their respective operating positions. In the machine of vertical spindle type, the speed indicating dial 2", shown in Fig. 1, has associated with it a pair of stationary indicators 263 and 284 corresponding to the positions assumed by the indicators 2" and 262 of the horizontal machine and bearing characters corresponding to the characters on the front of the spindle head 21 for indicating the fast and slow positions of the range changing knob 52.

The range changing couplet 244 in the horizonable knee 23 of the machine (as shown in Fig; 2) by means of a pair of vertically disposed splined shafts 2'll and2'l2 that have sliding engagement with the mechanism in the knee and that are driven, respectively, at feed rate and at rapid traverse rate. The feed rate shaft 21! is arranged to be driven only when the main clutch.

35 is engaged, in order that the work feeding mechanism may not be operated inadvertently when the tool carrying spindle is not rotating.

For this purpose, the driving power is derived from the main shaft 38 (as shown in Fig. 3) by means of the gear wheel I" fixed thereon and that meshes with a gear wheel 212 mounted on a stub shaft 214 which carries a bevel pinion 215 meshing with a similar bevel pinion 216. The

pinion 218 is splined on a shaft 211 which is con- 'nected by means not shown in the drawings,

to drive a bevel pinion 218, shown in Fig. 2, that meshes with a complementary bevel pinion 219,

on a vertically disposed sleeve 280. The sleeve 2" is provided at its upper end with a spur gear 2" that meshes with a spur gear 282 fixed on a sleeve 2" which is operatlvely connected to the upper end of the vertical shaft 21! for driving it.

Sinceit is desirable that the work supporting structure may be moved at rapid traverse rate regardless ofwhetheror not the spindle is oper-' sting, power for actuating the vertical rapid traverse driving shaft 212 is derived from the gear wheel Ill, Fig. 3, which is fixed on the sleeve m permanently connected to the main driving pulley 8|, whereby the gear I9. is driven whenever the motor 20 is operating. From the gear I", power is transmitted through a gear wheel 2" ends gear wheel- 28! constituting the driv-v ing train for the slow speed mechanism m, and

by means of other gearing (not shown in the drawings) to a bevel pinion 281, shown in Fig. 2, which meshes with a complementary pinion 288 on a' vertically disposed sleeve 28!. The sleeve 229 is provided at its lower end with a spur gear tal machine is constituted by separately formed gear and pinion elements, the pinion having formed integrally with it an internally and externally splined sleeve 266 arranged for sliding movement along a splined driving shaft 2" and adapted to receive the gear wheel 249. As appears in Figs. 12 and 13, the sleeve 2 presents a series of inwardly projecting lands 2 for slidably engaging the grooves in the splined shaft 261 and is provided with outwardly extending lands 268 which project into and enga e complementary splined grooves on the interior of the gear wheel 249. It is desirable that the pinion 250 be made as small'as possible andin order that the teeth of the pinion may be finished by rinding, the sleeve 2 is made smaller than the root diameter of the pinion with its walls formed as thin as possible. This is accomplished in this instance by disposing the internal spline landsfll Power for effecting actuation of the work supporting members is transmitted to transmission and control mechanism within the vertically movsleeve 2" joumalled in the saddle 24.

29B disposed adjacent to but supported independently from the adjacent to the feed shaft driving gear 282, the gear 2" being rotatably mounted on the sleeve 283 to which the feed gear 282 is fixed. From the idler gear 2". the rapid transverse transmitted to a meshing gear :92 fixed on the upper end of the vertical rapid traverse shaft 212 for driving it continuously regardless of whether or not the feed shaft 2'" is operating.

Fom the transmission and control mechanism in themes 22, power for actuating the work supporting table 28 is transmitted to a pair of bevel clutch gears 22! and 298 shown in Fig. 14 and arranged tobe driven in opposite directions respectively and mounted for free rotation on a sleeve 291 has splined connection with a table driving screw 29. that is rotatably mounted in the ends of the table 2! and has cooperative threaded engagement with a nut structure 299 mounted in the saddle 24, the arrangement being such that endwise feeding movement of the table is effected by rotary movement of the screw. Between the oppositely rotating clutch gears '29! and 2", there is positioned a clutch spool llll that has sliding splined connection with the sleeve 2" and that may be moved into clutching en gagem'ent with either clutch geartc couple it to the sleeve i'or driving the table in either direction-selectively. The clutch spool 3M may be moved along the sleeve 2", by means of a slid-- feed rate gear 2". The gear 290 meshes with an idler gear 29| that is disposed power is v The- . that are engaged by a pinion 308 slidably splined on a control shaft 333 that is rotatably mountedin the ends of the table 25. At its left end, the shaft 343 is provided with a pinion 3 l0 arranged to be actuated by a pinion 3 associated with another table controlling lever 3|2 which is pivotally mounted on the left end of the table and is accessible from the rear controlling position.

The table driving nut structure 239 mounted in the saddle 24 is madeadjustable for the purpose carefully turning the yoke byloosening one adjusting screw and tightening the other, the two screws serving to lock the nut, element in adjusted position.

Power for actuating the sliding head 21 to effect vertical feeding movement of the spindle 28 is also derived from the transmission mechanism 'gears 332 and 333 that are rotatably mounted of maintaining close engagement with the table 7 driving screw 238 to adapt the machine to climb cutting operations As best shown in Fig. 16, the nut structure comprises two parts, one of which is a fixed nut element3l5 that has screw threaded engagement with a receiving bore 3 l 6 in the saddle 24 and that is locked rigidly in the saddle by a locking screw 3". The other nut element is in the form of a cylindrical member 3l8 that is rotatably received in the bore 3| 3 and that is normally positioned to abut the inner end of the stationary nut element 3l5. As best shown in Figs. 16 and 1'7, the outer end of the adjustable nut element M3 is provided with circumi'erentially arranged serrations 3|3 adapted to cooperate with complementary internal serrations 328 in a nut'adjusting yoke 32l.

In adjusting the nut mechanism 233 to take up lost motion between it and the screw 238, the

adjustable nut element 3| 8 is turned upon the screw 233 to bring it into abutting relationship with the fixed nut element 3| 5. After a coarse adjustment has been effected in this manner, the nut adjusting yoke 32] is fitted on the'serrated end of the nut element 3|8 in the position shown in Fig. 17. A pair of lugs 322 and 323 projecting at opposite sides of the yoke 32| are then engaged by adjusting screws 324 and 325 threaded in the saddle structure 24. By turning the adjusting screws 324 and 323, the adjustable nut element 3" may be turned on the screw 293 under positive control for effecting close adjustment of the degree of engagement between the nut mechanism 233 and the screw 238. With the of the screw threads in the adjustable nut element 3l8 are brought into contact with the right faces of the threads on the screw 238, as shown in Fig. 15, while the right faces of the threads in the fixed nut element 3| 5 are caused to engage the left faces of the threads of the screw.

concentric with a vertically disposed nut actuatto the shaft 334 for turning itin either direction selectively, by means of a clutch spool 335 slidably splined on thevshaft between the gears. As best shown in Fig. 7 the vertical shaft 334 is provided at its upper end with a spur gear 336 that meshes with a horizontally disposed idler gear 331 which meshes in turn with a gear 333 formed on a rotatable nut 339 that is journalled in the column structure by means of anti-friction bearings 340. ,As shown, the rotatable nut 333 has threaded engagement with a vertical disposed elevating screw 34] that is connected at its lower end to the sliding head structure 21, whereby the head may be raised or lowered upon rotation of the nut 333 in the one or the other direction.

For controlling the direction and the extent of power movement of the sliding head 21, a hand lever 343 is pivotally mounted on the right side of the column adjacent to the head, as shown in Fig.2. The hand lever is operatively connected by linkage 344, shown in Fig. 9, with a vertically movable shifting fork 345 -which engages the engagement with trip posts 343 and 353 whichconnect with the linkage 344 and operate to disengage the clutch spool 335 to stop the head at either of two predetermined limiting positions in nut structure thus closely adjusted, the left faces its path of travel. A multiple position stop mechanism 35l is also provided on the sliding head 21 in position to cooperate with a trip rod 352 for stopping the head at a selected one of a plurality of predetermined positions in the course of downward feeding movement of the spindle 28. For effecting manual vertical movement of the sliding head 21, a hand wheel 353 is provided on the forward end of a bracket 354 projecting from the column, the hand Wheel being connected by a shaft; 355'with a bevel pinion 356 which meshes with a similar bevel pinion 351 on the lower end of the vertical shaft 334 for turning it to effect actuation of the head elevating nut 333.

From the foregoing detailed description of the.

illustrative structures set forth herein to disclose the principles of the present invention, it is apparent that there has been provided an improved power transmitting and controlling mechanism for actuating. the movableparts of 'a machine tool, including improved elements of machine stnlicture especially adapted for use in machine 

